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S 2149 
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Grain Dust Explosion 
Prevention 



UNITED STATES GRAIN CORPORATION 

In Co-operation with the 
Bureau of Chemistry 

UNITED STATES DEPARTMENT OF AGRICULTURE 



DUST from grain will explode when 
mixed with air in proper propor- 
tions and ignited by sufficient heat 
or flame. The hazards of a dusty 
and dirty plant are very great. The 
only safe guaranty against a dust 
explosion is to practice "good house- 
keeping " and keep your plant clean 
at all times. It is your duty to 
protect not only your property but 
the health and lives of your employes 



a-r'^ 



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NEW YORK 

June 1920 



n. ©f iP* 

Nuv 13 1921 



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ORGANIZATION OF DUST EXPLOSION PREVENTION 

CAMPAIGN 

In carrying on the dust explosion prevention campaign for the year 
1919-20 the United States was sub-divided into four districts: Eastern, 
Northwestern. Central and Pacific Coast. The personnel of this cam- 
paign was as follows : 

UNITED STATES GRAIN CORPORATION 
Dr. J. W. T. DuvEL, New York, in Charge 

Mr. H. E. Roethe, Jr Washington, D. C. 

Mr. J. O. Reed Washington, D. C. 

Mr. H. R. Brown Washington, D. C. 

Mr. G. D. Wither Washington, D. C. 

Mr. E. L. Riley Buffalo, N. Y. 

Mr. p. L. Mann New Orleans, La. 

Mr. Vernon Fitzimons Minneapolis, Minn. 

Mr. Paul E. Brady Minneapolis, Minn. 

Mr. W. B. Lind Minneapolis, Minn. 

Mr. G. a. Hibbard Chicago, 111. 

Mr. G. H. Rice Chicago, 111. 

Mr. H. J. Helmkamp Kansas City, Mo. 

Mr. M. E. McCollam San Francisco, Cal. 

Mr. G. p. Bodnar Portland, Ore. 

U. S. DEPARTMENT OF AGRICULTURE 

Mr. D. J. Price, 

Engineer in Charge of Dust Explosion Investigations. 
U. S. Bureau of Chemistry, 
Washington, D. C. 

Dr. H. H. Brov^n, 

Organic and Physical Chemist, 
U. S. Bureau of Chemistry, 
Washington, D. C. 



GRAIN DUST EXPLOSION PREVENTION 



CONTENTS 



PAGE. 

Introduction 5 

Educational Work 6 

Pledge cards 7 

Meetings in grain center 9 

Cooperation with Canadian Government 9 

Inspection of Plants 9 

Improvement in condition of plants 13 

Literature 15 

Results of Campaign 18 

Explosions during Campaign 19 

Buffalo, N. Y 19 

Port Colborne, Ont., Can 20 

Kansas City, Mo 21 

Spice dust Explosion 22 

Aluminum dust Explosion 23 

Boissevain, Man., Can 24 

Buffalo, N. Y 24 

Denver, Colo 25 

Experimental Work 25 

Theory of dust explosions 25 

Density of dust cloud 25 

Source of ignition 26 

Velocity of propagation of explosion 26 

Pressures developed in explosions 26 

Conditions for explosions 26 

Propagation of the explosions 26 

Prevention of explosions 27 

Large scale tests 27 

Electrical equipment and dust explosions 2S 



GRAIN DUST EXPLOSION PREVENTION 



INTRODUCTION 



The Government first gave consideration to the dangers from grain 
dust explosions and fires, as a result of a disastrous explosion in a feed 
grinding plant at Bufifalo, New York, in 1913. As a result of this explo- 
sion, a series of investigations were conducted by the Bureau of Mines 
of the United States Department of the Interior, in cooperation with 
the milling and grain interests, with the view of determining the causes 
of such explosions and fires, and to devise methods for their prevention. 
Subsequently this project was turned over to the Bureau of Chemistry 
of the United States Department of Agriculture, and much valuable 
information brought together relative to explosions and fires in grain 
elevators, flour mills, threshing machines (^) in the Pacific Northwest 
and in cotton gins(^) of the South. 

The importance of continuing and extending these investigations was 
fully realized at the beginning of the war, in order that the country's food 
supply might be fully protected against the hazards of dust explosions 
and fires. Accordingly the United States Department of Agriculture and 
the United States Food Administration inaugurated an extensive educa- 
tional campaign, in the Fall of 1917, to provide the owners and operators 
of mills, elevators and threshing machines, with the information avail- 
able, so that the losses resulting from dust explosions might be reduced 
to a minimum. The necessity for this undertaking was strongly empha- 
sized by several disastrous dust explosions which occurred between 
March, 1916, and October, 1917, resulting in the destruction of four of 
the largest grain and cereal plants in the United States and Canada, to- 
gether with the loss of twenty-four lives. The dust explosion, together 
with the fire which followed, in one of these plants (Brooklyn, New 
York), was of special significance at the time in that it resulted in the 
destruction of a quantity of grain equivalent to bread rations for an army 
of 200,000 men for an entire year, and at the same time most seriously 
crippled facilities badly needed for loading grain for overseas shipment. 



(a) Department of Agriculture Bulletins 379 and 681, and Circular 

(b) Department of Agriculture Circular No. 28. 



The workmen in this plant were not generally familiar with the causes of 
dust explosions and fires and methods that could be adopted for their 
prevention. 

The United States Grain Corporation assumed financial control of 
the grain dust explosion campaign in July, 1919, to make sure that the 
Government's stocks of wheat were fully protected at all times ; other- 
wise the work would have lapsed June 30, 1919, with the termination of 
the war emergency provision granted by Congress to carry on this work 
as a part of the food conservation program. Since this time, the United 
States Grain Corporation, in cooperation with the Bureau of Chemistry 
of the United States Department of Agriculture, has carried on an exten- 
sive campaign to assist in removing dangerous conditions in plants carrying 
Government grain and flour stocks, and also to familiarize the grain and 
milling interests with the true nature and means of prevention of dust 
explosions and fires. The aim has been to lessen the inherent hazards 
in the grain industry. Throughout this campaign active cooperation has 
been given by many agencies and commissions engaged in explosion and 
fire prevention activities, and this opportunity is taken to acknowledge 
our indebtedness to these organizations, as well as to the grain and mill- 
ing interests, for the excellent assistance rendered. 



EDUCATIONAL WORK 

In addition to the regular inspection of plants carrying Government 
stocks, an efifort was made to impart to the employes of elevators and 
mills special information on the subject of dust explosions and fires. In 
the war emergency campaign all mills with capacity of approximately 50 
barrels or more, and elevators over 25,000 bushels capacity, were visited. 
In the campaign carried on by the Grain Corporation attention has been 
directed primarily to plants where Government stocks were stored. The 
work has been extended, however, to outside plants as time permitted. 

The employes in the plants were acquainted with the causes by which 
explosions can be produced, with special reference to the simple causes 
within the control of the workmen, such as a lighted match, smoking, use 
of open flames, careless use of electric lights, etc. This was done in 
many cases by a direct " heart to heart " talk with the men either indi- 
vidually or in group meetings, on the working floors or in convenient 
parts of the plants. In order to familiarize the men with the extent of 
damage done by previous explosions, a series of specially prepared photo- 
graphs showing views of damaged plants in which there had been ex- 
tensive losses of life, grain and property were used. 

Whenever it was possible to assemble a number of the employes, 
either at the noon hour, or by special arrangement with the management, 
illustrated lantern slide lectures, showing results of experimental work, 
and also efifects of recent explosions, similar to photographs referred to 

6 



above, were given. In addition to the lecture, various demonstrations 
of dust explosions were produced to show the men how readily a violent 
explosion may result from an apparently simple cause. Two demonstra- 
tions in particular impressed the men effectively and aroused their 
interest. In one case a dust explosion was produced in a specially pro- 
vided miniature grain elevator by blowing dust onto an open flame, as 
shown in Figure 1. In the other, various common dusts were readily 




Fig. 1. Dust Explosion Demonstration — produced by blowing dust into an open flame in a 

miniature elevator. 

ignited by sifting through a piece of cheesecloth onto a burning match. 
In order to remove any doubt regarding the nature of the dust used m 
the demonstrations, the workmen were asked to collect dust from various 
parts of the plant. In many instances samples of the dust which the 
employe had to work with and handle daily were presented for testing. 
The effect of the explosion on the workmen in these cases was very 
marked. From expressions made by the men it could be seen that they 
would not forget the lesson and would do all they could to prevent 
dangerous conditions. 



Pledge Cards 

At the close of the lecture and demonstrations, or during the inspec- 
tion trip through the plant, the moral support of the workmen was 
enlisted by having them sign pledge cards as shown in Figure 2. 



UNITED STATES DEPARTMENT OF AGRICULTURE 

AND 

UNITED STATES FOOD ADMINISTRATION 



HAVE ALREADY SIGN 



) A FELLOW EMPLOYEE) 



To prevent grain dust explosions and fires in the mills and elevators in which 
I am employed, 1 agree personally to obser\'e preventive measures and to use 
every effort and influence to induce others to lake all possible precautions. 1 
make this promise in the realization that carelessness rnay result in loss o( life, loss 
ot (ood needed by the Nation, and destruction ol factories needed to produce food. 



Name 

Firm or Company- 
City — 



Failure to observe tKeee 
nay result in dust explosions or fires wh: 
nay cause loss of life and will cause loss 
ood needed by the Nation: I 

1. Smoking and ligVited matches hi 
au&ed many of our greatest fires and 



mutches 



r th» 



i dusty mill or elevator. 



3. Dust and dirt invite dust explosion 
The records show that there are six tim( 
as many 6res in dirty mills and elevators i 



pulleyi. 



[ whei 






4. Elevator choke-ups are frequent 
causes of fires and explosions. In many 
cases choke-ups have led to fires which 
destroyed over a million dollars' worth of 
grain and property, 

all elc 






the; 



vol.. rvia 



• Mgh 
ouble. 



.ently 



Fig. 2. — Pledge card signed by workmen. 

(a) Front of card. 

(b) Back of card. 



A ready response was always secured and large numbers of these 
cards were signed by the employes. By so doing they promised to observe 
the precautions designed for the prevention of these explosions. The 
cards were forwarded to the Washington office, and their receipt imme- 
diately acknowledged, with the name and address of the workmen in- 
serted on the card, as shown in Figure 3. It is believed that the work- 
men adhered to their promises and were responsible in many instances 
for the removal of dangerous conditions which might have resulted in 
explosion and fire. 



UNITED STATES DEPARTMENT OF AGRICULTURE 

AMD 

UNITED STATES FOOD ADMINISTRATION 

Washincton, D. C. 

llr. iToe Taylor, 

540 Tlorth T>unoaii Gt., 
Chioago, 111. 
Dear Sir: 

This is to acknov^ledge receipt of the card, recently signed by you, in which 
you personally agree to observe preventive measures and to use every effort and 
influence to induce others to take all precautions to prevent grain-dust explosions 
and fires in mills and elevators in which you are employed. By signing this card 
and carefully observing the pledge made thereon, employees of mills ancl elevators 
are actively cooperating with the United States Department of Agriculture and 
the United States Food Administration in their effort to SAVE FOOD AND 
WIN THE WAR. 




HERBERT HOOVER 
lyP Food Administrator 




D. F. HOUSTON 
Secretary of Agricuitu 



Fig. 3. — Card acknowledging pledge of workmen. 

8 



Meetings in Grain Centers 

In addition to presenting the dust explosion prevention work to 
the employes in the plants, it was considered desirable to acquaint the 
owners and operators with the hazards. As it was impossible to stage 
large-scale demonstrations all over the country, specially arranged motion 
pictures showing the results of large scale dust explosion tests, as de- 
scribed on page 27 , were shown to the grain men in various sections 
of the United States. While the small scale demonstrations of dust 
explosions served their purpose well, they did not show fully the rate at 
which an explosion might propagate through the plant. The motion 
picture reels also contained views of plants damaged by explosions and 
fire together with measures of prevention. The work was also pre- 
sented at conventions of fire protection, conservation, and similar asso- 
ciations. These conventions in many instances included not only grain 
men but firemen and insurance representatives as well. Numerous re- 
quests for presentation of the work were received from associations of 
firemen, in order to obtain information to assist in the prevention of dust 
explosions during the progress of fire fighting. 



Cooperation with Canadian Government 

In connection with the series of meetings held in the larger grain 
centers of the United States, as a result of a request from the Domhiion 
Fire Commissioner, a special dust explosion prevention meeting was 
held at Fort William, Ontario, in November, 1919. This meeting was 
attended by a large number of Government, provincial and city officials, 
as well as representatives of the Canadian grain and milling industries 
and insurance companies. 

Interest in dust explosion prevention was aroused in Canada by 
an explosion in August, 1919, in a large grain elevator at Port Colborne, 
Ontario, operated by the Dominion Government. The explosion was in- 
vestigated in cooperation with the Canadian Government officials and 
assistance rendered in the development of precautionary measures in 
the rebuilding of the plant. 



INSPECTION OF PLANTS 

As previously stated, this campaign was undertaken primarily for 
the protection of the Government grain and flour stocks against the 
hazards of dust explosions and fires. For this purpose, regular inspec- 
tions were made of the mills and elevators where Grain Corporation stocks 
were stored. Other plants were likewise visited frequently in order that 
the country's food supply might be fully protected. If conditions seemed 
hazardous in any respect, definite suggestions for remedying them were 



made to the official in charge of the plant. At the time of the first visit 
to each establishment, the inspector filled out a complete report on the 
following form provided for the purpose : 



GRAIN DUST EXPLOSION CAMPAIGN 

U. S. DEPART JIENT OF AGRICULTURE 

BUREAU OF CHEMISTRY AND BUREAU OF MARKETS 



District Date Inspected by 

Name of Company 

Office Address: Street City ' State 

Plant Address: Street City State 

Kind of Plant Mgr 

Supt Capacity No. Employees 

Construction: Wood Brick or Stone Concrete Steel. 

Remarks 

Bins : Open Covered Remarks 

Elevators : Wood Steel Combination 

Discharge to Bin: By Spout Belt Steel Conveyor. . . . 

Remarks 

Is Grain Cleaned before Storage? Yes No 

Remarks 

Dust Collectors : Location Cloth 

Cyclone Dust Room 

Remarks 

Suction System: On Bins Elevator Heads Conveyors 

Remarks 

Grinding Mills : Type 

Discharge to: Elevator Conveyor Bin 

Misc 

Any E.xplosion Protection 

Remarks 

Power Plant: Steam Electric Gasoline Misc.. . 

Lighting : Type Method of I nstallation 

Remarks 

General Condition of Plant 

Remarks 

Are Sweepers Employed ? 

General Remarks 



No. of Cards Signed No. of Circulars Desired. 

No. of Posters Desired 

Suggested Recommendations for Explosion and Fire Prevention 



Copies of this report were then sent to the district office and also to 
Washington, where they were recorded. On all subsequent visits the in- 
spector used a shorter form on which he noted only the rating for equip- 



10 



ment and maintenance and, when necessary, his recommendations to the 
company, as well as any changes in equipment since the preceding inspec- 
tion. 



GRAIN DUST EXPLOSION AND FIRE PREVENTION 

V. S. GRAIN CORPORATION 

U. S. DEPARTMENT OF AGRICULTURE 



District Date Inspector 

Name o£ Company 

Address: City State 

Manager Supt 

Kind of Plant Capacity 

Equipment Maintenance No. Employed. 

Recommendations Made to 

Recent Changes, Recommendations, etc 



In making these reports the following series of letters was used to 
classify the equipment and maintenance of the plant: 

Equipment Maintenance 

A. Modern, first-class, up-to-date appliances A. Good 

B. Fair, not new. ^- ^^^^ 

C. Old and not representative C. Poor 

A well-constructed plant, with modern mechanical appliances, would 
be given "A" for equipment. If precautionary measures were being 
carried out, and the explosion hazard recognized, the plant received "A" 
for maintenance. The classification for such a plant would then be 
"A A." If the maintenance was not up to the standard and the dust con- 
ditions looked after in only a " fair " manner, the classification would be 
" AB." If the plant was well equipped, but found in a dirty, dusty, or 
poor condition, it would receive a grade of " AC." In many cases, how- 
ever, equipment which was not strictly modern but was rendering satis- 
factory service was put in the " B " class, to distinguish it from that of 
newer type or design. If the plant was well maintained it would be 
classed as " BA," while " BB " and " BC " represented the intermediate 
and poor classes, respectively. Old type plants, in which the equipment 
had been installed for some time fell in the " C " class. When it was 
well maintained and particular attention was paid to the removal of the 
dust conditions, the plant would be placed in the " CA " class. Similarly, 
" CB " and " CC " represented the other grades of upkeep and mainte- 
nance. 

11 



United States 
Department of Agriculture 



SAVE LIVES 



United States 
Food Administration 



SAVE FOOD-SAVE PROPERTY 




Six Recent Dust Explosions and Fires in Mills and Elevators 

Killed 39 Persons and Injured 60. They Destroyed 2,500,000 

Bushels of Grain, and Property Worth $8,000,000 



Keep Your 

Mill and 

Elevator 

Free from 

Dust and Dirt 




Dust-free 
Mills and 
Elevators 
are Eixplo- 
sion-proof 



Viitf niwiiii: 

Elevator explosions and fires soiiietiwes destroy enough grain to feed a large army far a year 



<.<Zil£=i,'i' 





PROTECT YOUR MILL AND ELEVATOR 

yi little care way avert a disastrous explosion. Observe the fbllozvtng rules: 

1. Do not smoke or carry matches in or near the buildings. y Do not let dust accumulate on beams, machines, pulleys 
Smoking and lighted matches cause explosions and fires. or floors. Dust-free Mills and Elevators are explosion -proof. 

2. Do not use open flames, torches, candles, lanterns and un- 4. Examine elevators and conveyors often. Elevator choke-ups 
protected electric light bulbs in a dusty atmosphere or when often cause explosions and fires. Report immediately any slight 
examining bins and elevator legs. rubbing, slipping, or other trouble. 



For furl her itiJorma:iim rtgjrdiiig grain Jus! txplostont virile 10 ihe 

U. S. Department oF Agriculture, Bureau of Chemistry, Washington, D. C. 

This Company and iu Employees are Co-operating in the Control of Dust Explosions and Fires 



Fig. 4. — Reproduction of first poster used in Grain Dust Explosion Prevention Campaign. 

(Original 16 x 24 inches.) 



12 



These reports also were sent immediately to district headquarters and 
then to Washington, so that the officials in charge could at all times keep in 
close contact with the general conditions of the mills and elevators 
throughout the country. By comparison with previous reports, it was 
possible to determine whether or not the condition of the elevator was 
improving and whether the precautionary measures previously recom- 
mended had been adopted. 

Improvement in Condition of Plants 

That conditions in the elevators and mills inspected were materially 
improved as a result of the recommendations made to the officials in 
charge is evident from the reports turned in by the field men. The fol- 
lowing table gives a few typical cases of the results of this phase of the 
work. 

Elevator Visit Date Grade 

1 1 September 4, 1919 AC 

(Middle West) 2 September 26, 1919 AB 

3 February 18, 1920 A A 

? 1 September 23, 1919 AC 

(East) 2 November 29, 1919 AB 

3 March 5, 1920 AA 

3 1 November 26, 1919 BC 

(East) 2 March 1, 1920 BB 

3 March 20, 1920 BA 

4 1 September 11, 1919 CC 

(West) 2 October 17, 1919 CB 

3 February 4, 1920 CA 

5 1 August 19, 1919 AA 

(East) 2 December 17, 1919 A A 

3 Jamiary 28, 1920 A A 

4 April 13, 1920 A A 

Elevators 1 and 2, although well constructed and equipped with 
modern machinery, were poorly maintained at the time of the first inspec- 
tion. As a result of following the recommendations made by the inspec- 
tor, conditions were so improved that when the last inspection was made 
the plants received the grade of " AA." 

Although elevator 3 remained in class " B " (medium) for equip- 
ment, it improved sufficiently in condition to rise from " C " to "A" in 
maintenance. 

Elevator 4 was poorly equipped and very poorly maintained at time 
of first inspection, showing evidence of but little precaution against fires 
and explosions. The information received by the officials, however, en- 
abled them to bring their grade up to " B," and finally, after they had 
adopted additional methods of dust explosion and fire prevention, to " A," 
the equipment in this plant was not improved, remaining in the "' C " 
grade. 

Elevator 5, modern in construction and equipment, was found at the 
time of each visit to be in an excellent condition and provided with every 
device for minimizing the dangers from dust explosions. 

As this summary is representative of the large number of reports 
received from all over the country, it may be concluded that the recom- 

13 



Dust- Free 

Mills and ElGvators 

are EXPLOSION" 

Proof 




Carelessness 



a lighted match 
dusty machinery 
an uncovered candle 

or lanteiTi 
friction in machineiy 



Cleanliness 



means nothino to 

explode " 
protects workmens' lives 
saves property 
saves food 




U.S.Grain Corporation- 

U.S.Depaitment of Agriculture 

For further information about grair\ dust explorionj write to the 
Bureau of Chemistry, - U . S. Departmer\t of Agvicultuve. 



Fig. 5. -Reproduction of lecond poster used in Grain Dust Explosion Prevention Campaign. 
(Original in colors, 14'4x22 inches.) 



14 



mendations made in this campaign brought about an improvement in 
conditions and a decrease in dangers from explosion and fire in the 
elevators and mills of the United States. 



LITERATURE 

To keep the dangers from explosions and fires before the men at all 
times, two sriking posters (Figs. 4 and 5) were prepared. These posters 
were mailed to every licensed elevator and mill and also distributed 
through the conservation and fire prevention agencies. They were dis- 
played in prominent parts of the plants and in the frequent visits to the 
elevators and mills it was found that the workmen were following the 
precautions outlined. 

Several pamphlets were also provided for the workmen to read dur- 
ing their lunch hours or at any spare moments. In the circular entitled 
" Prevent Grain Dust Explosions and Fires" (Fig. 6) attention was di- 
rected to the great loss of life, property and foodstufifs due to dust explo- 
sions, and a brief description is given in simple language of how a dust 
explosion actually occurs. The employes were asked to help reduce this 
loss by observing the following rules: 



PREVENT GRAIN DUST 
EXPLOSIONS AND FIRES 

IT IS POSSIBLE— NECESSARY 




This Ciitiilar Tcllo How and Why 

V. S. DEPARTMENT OF AGRICULTURE 

WASHINGTON, D. C 
1918 



Fig. 6. 



1. Get the dust. 

2. Prohibit smoking and carry- 

ing matches in or around 
the mill or elevator. 

3. Use no open flames, as gas- 

lights, torches, lanterns or 
candles for any purpose 
whatever in or around the 
mill or elevator. 

4. See that all wires for electric 

lighting are placed in con- 
duits, and use only well- 
protected globes. 

5. Do not lower artificial lights 

into bins to determine the 
amount of grain, flour or 
feed they contain. 

6. Keep all foreign material 

from entering the grinding 
machinery. 

7. Eliminate static electricity. 

8. Look out for elevator choke- 

ups. 

9. Do not let elevator or con- 

veyor belts rub. 

10. Sack the ground material im- 
mediately or convey it to 
bins of small capacity. 



15 



lust a Word 



"Just a Word About Grain Dust Explosions" (Fig. 7) contains a 
summary of the dust explosion campaign preceding September, 1919, 
pointing out that for a period of 19 months there were no explosions in 
plants where the workmen had pledged their support to the work, while 
disastrous explosions had occurred in other industries. It includes eight 
short stories describing eight explosions, illustrated with attractive draw- 
ings, and gives the cause and method of prevention in each case. It fur- 
ther urges employes to adopt 
the following dozen rules 
for safety: 

1. Keep the plant clean. 

2. Inspect the plant frequently 



for hot bearings. 

3. Keep constantly on the watch 

for elevator choke-ups. 

4. Report immediately any 

slight rubbing, slipping or 
other trouble with belts or 
machines. 

5. Keep all foreign material 

from entering the grinding 
machinery by installing a 
magnetic separator. 

6. Do not smoke while in or 

near the elevator. 

7. Do not carry matches in or 

near the buildings. 

8. Do not allow an open flame, 

lantern or torch in the mill 
or elevator. 

9. Do not lower artificial lights 

into bins to determine the 
amount of grain, flour or 
feed they contain. 

10. Prevent the accumulation of 

static electricuy on ma- 
chines and belts by proper 
grounding methods. 

11. See that all electrical equip- 

ment is properly installed, 
light bulbs well protected, 
switch and fuse boxes kept 
closed. 

12. Sack the ground material im- 

rnediately or convey it to 
bins of small capacity. 







Fig. 7. — Upper purliun of this plant dc^tKiycd by 
dust explosion. From cover-page of pamphlet 
used in educational campaign. 



Two small folders were designed to call attention, in a few words 
and by means of pictures, to the dangers of dust explosions and to some 
of the simple preventive measures. The folder entitled " Four Reasons 
Why You Should Be Careful " (Fig. 8), urges the employee to follow a 
few important rules for the protection of life, property, food and his 
job. The other, commonly called the " Capitol Folder," emphasizes the 
cost of carelessness, and endeavors to impress upon the employee by a 
specially prepared story, the fact that one careful man in a plant is better 
than a whole fire department. It contains four rules for the protection 
of lives, food and property from the dangers of dust explosions. 



16 




REASONS 
WHY YOU 
SHOULD BE 
CAREFUL 



REASON No. 3 




Loss of 
Food. 



REASON No. 1 




Loss of 
Property. 



REASON No. 2 



REASON No. 4 



s^^ 



^ 




Loss of 
Job. 




Loss of 
Life. 



HOW TO 
BE CAREFUL 

Look over the elevators and 
conveyors often, report at once 
any rubbing, slipping, friction, or 
other trouble, no matter how 
slight. 

Also observe carefully these 
four important DON'TS : 

Never smoke in or near 

the mill or elevator. 
Never strikai a match any- 
where on the premises. 
Never use open flames, 
torches, candles, lan- 
terns, or unprotected 
light bulbs in dusty air 
or when examining bins 
or elevator legs. 
Never let dust accumulate 
on beams, machines, 
pulleys, or floors. 

UNITED STATES GRAIN CORPORATION 

Cooperating with the 

UoUed Slates Deparunent of Agriculture 

Bureau of CbemiBtry 



Fig. 8.— Reproduction of small folder used in educational campaign to prevent destruction 
of Government food supplies by dust explosions and fires. 



17 



RESULTS OF CAMPAIGN 

The dust explosion and fire prevention work was well received in 
every section of the country. With the splendid cooperation of the 
American mills and elevators, as well as the various fire prevention 
agencies and commissions established to conserve our food supply, the 
campaign was most successful. During the entire period of its existence 
(about three years) the United States Grain Corporation sufifered no 
extensive explosion or fire losses. The fact that practically at all times 
the value of the stocks in storage was $100,000,000 and at certain times 
approximately $500,000,000, shows the importance of the saving thus 
effected. 

During the period of the campaign there has been only one disastrous 
explosion in a grain elevator where United States Grain Corporation 
stocks were stored. The actual loss to Government grain in this case, 




Fig. 9. — Extensive damage resulting from explosion of starch dust. 

however, was limited to about $25,000. Since this explosion in Septem- 
ber, 1919, there has not been an explosion in the last nine months in a 
plant where Government grain was stored or handled, and where atten- 
tion had been given to the removal of explosion and fire hazards. 

While the explosion and fire losses in the grain industry appear to 
have decreased during this special campaign period, reports indicate that 
in other industries the fire losses were considerably increased. In May, 
1919, a very disastrous explosion in a starch factory in the Middle West 
resulted in the loss of 43 lives and property damage estimated at $3,- 
000,000. The wreckage of this explosion is shown in Figure 9. In 
August, 1919, a large grain elevator operated by the Canadian Govern- 

18 



ment was badly damaged by a dust explosion in which 10 lives were lost 
and 10 injured. An explosion of aluminum dust in a factory in Wis- 
consin caused the death of six girls and injuries to as many others. Ex- 
plosions of minor proportions have occurred during the period in feed 
mills, flour mills and other industrial plants. 

The effect of enlisting the aid of the workmen is shown by the fact 
that during a period of 19 months (October, 1917, to May, 1919) no 
dust explosions occurred in any of the plants where the employees had 
pledged their support to the campaign. In marked contrast to this are 
the five disastrous explosions in the United States and Canada of the 
preceding 20 months (March, 1916, to October, 1917). 



EXPLOSIONS DURING CAMPAIGN 
Buffalo, N. Y. 



On September 12, 1919, 
a dust explosion in a feed 
mill and elevator at Buffalo. 
New York, injured 3 men, 
1 seriously, and damaged 
property to the extent of 
$20,000 (Fig. 10). 

The investigation showed 
that the force of the explo- 
sion traveled upward, blow- 
ing out a part of the west 
wall of the fourth floor as 
well as part of the roof of 
the lofter room at the top of 
the building, and that a mus- 
lin cover used to keep one 
of the motors on an upper 
floor free from dust had 
been burned. At first it 
was thought that the explo- 
sion was caused by the igni- 
tion of this muslin cover by 
sparks from the motor. A 
detailed observation of the 
motor, however, showed 
that no sparks issued from its brushes while it was in operation, and that 
it worked satisfactorily, thus making it apparent that the motor cover 
was set on fire by the explosion. From the nature of the damage it 
seemed that the explosion originated from an unknown cause at some 
point on the first floor near an elevator leg, and propagated up to the 
fourth floor where a second and more disastrous explosion occurred. 

19 




Fig. 10. — Damage to upper floors resulting from dust 
explosion in a feed mill. 




Port Colborne, Ontario, Canada 

On August 9, 1919, an explosion occurred in an elevator owned and 
operated by the Canadian government at Port Colborne, Ontario, Canada, 
as a result of which 10 men lost their lives and the same number were 
more or less seriously injured, while the loss of property was estimated 
at $750,000 (Fig. 11). 
The damage 
wrought by the explo- 
sion was confined to 
the area above the 
storage tanks, very 
little damage being 
done to the basement 
and storage section of 
the plant. The bin 
floor and the roof 
over the storage sec- 
tion were entirely 
blown ofif. Part of 
the side walls of the 
working tower was 
demolished, as well as 
a large portion of the 
roof of the working 

house. Both ends of the tower were badly damaged. In fact, the force 
of the explosion at these points was so great that heavy 8-inch steel " I " 
beams were carried some distance from the plant. In some cases large 
pieces of reinforced concrete were hurled for a distance of 150 feet. A 
barge which was being loaded with grain in the slip on the east side of 
the plant was sunk by the large quantity of debris which was thrown 
upon it. 

From the evidence obtained in the investigation it would seem that 
the explosion was the direct result of a choke-up which occurred in an 
elevator leg. Before the choke-up was noticed and the motor stopped, so 
much friction had developed at the head of the elevator that the belt 
began to smolder and burn, until it parted and dropped down through 
the legs into the elevator boot and well. The dense dust cloud raised in 
the legs and well was ignited by the smoldering or burning ends of the 
belt. The explosion then propagated through a small opening in the well 
to all sections of the plant. On account of the peculiar trough plate con- 
struction of the sides of the bins a great deal of dust had accumulated 
on the bin walls. This dust, thrown into suspension by the force of the 
first explosion, was ignited by the flame which traveled through the open- 
ing between the tops of the bins and the bin floor. Since all the bins 
were connected, the explosion blew away the entire upper portion of the 
plant. 



Fig. 11. — Upper portion of grain elevator badly damaged by dust 
explosion. Note " trough-like " construction of interior 
walls of bins. 



20 



Kansas City, Mo. 

In a very disastrous explosion which occurred September 13, 1919, 
in a large terminal elevator at Kansas City, Mo., 14 men lost their lives 
and 10 were seriously injured (Figs. 12 and 13). The elevator was par- 




FiG. 12. — View showing violence of explosion and damage to working floor and shed. 
Explosion originated in basement. 




Fig. 13. — Explosios trareled from basement through man-lift tower to " texas " or top 

of elevator. 

21 



tially wrecked, the property loss being estimated at $650,000. This ex- 
plosion was not confined to any one portion of the elevator, but propa- 
gated to all sections of the workhouse. 

The evidence at hand indicates that the explosion originated in the 
basement, in the vicinity of one of the receiving legs, where workmen 
were cleaning up the plant. Great difificulty was encountered in determin- 
ing the exact cause of the explosion, owing to the fact that all the evidence 
required to establish it had been destroyed on account of the force of the 
blast. Judging from the violence of the explosion, the dust in this plant 
must have been very inflammable. 

The evidence secured from one of the workmen indicated that the 
source of ignition may have come from an electrical short circuit. This 
workman stated that he heard a sharp cracking noise shortly before the 
explosion, and thought that he had seen blue flashes of flame traveling 
along the electric light wires. The short circuit may have been caused 
by defective extension cords or the breaking of an unprotected lamp 
bulb in the dusty atmosphere present. Workmen in the basement were 
known to have been using extension cords at the time of the explosion, 
and it is possible that ignition came from such a source. 

Spice Dust Explosion 

On January 17, 1920, 4 firemen were killed and 13 injured, 3 of them 
very seriously, when an explosion in the burning mills of a spice company 
in Cincinnati, Ohio, blew out the east wall of the structure (Fig. 14). 




Fig. 14. — At extreme right can be seen bridge from which firemen were fighting the fire 
when the wall was blown out by explosion of spice dwst. 

22 



Since the early newspaper reports stated that the disaster was due 
to an explosion of tea and spice dust, an investigation was conducted to 
determine if possible the true cause of the explosion. From the evidence 
that was secured it seems that the walls of the building fell without any 
warning. Tests showed the spice dust to be very inflammable, and it is 
reasonable to conclude that the explosion or force which blew out the 
walls of the plant was probably due to the ignition of a cloud of spice 
dust which was formed when the floors in the building fell. 

Aluminum Dust Explosion 

On February 26, 1920, a disastrous dust explosion occurred in an 
aluminum goods manufacturing plant at Manitowoc, Wis., as a result of 
which 6 girls lost their lives and 5 were seriously injured (Fig. 15). 




Fig. is. — View of dust collecting system showing wire as found in fan following the 
explosion. Buffing brushes used can be seen on bench. 

The explosion originated in a dust-collecting system used in collect- 
ing the fine particles of aluminum dust which are given off during the 
process of putting the satin finish on aluminum goods. This process 
consisted in holding the aluminum article against a rapidly revolving steel 
brush. 

The cause of the explosion is attributed to a piece of No. 7 iron wire 
winding itself around the blades of a blower fan. This produced a spark 
which ignited the fine particles of aluminum dust in suspension in the 
fan and gave rise to the explosion. 

23 



These and other like disasters should lead the chiefs of the city fire 
departments to make an earnest effort to acquaint themselves and their 
men with the nature of dust explosions occurring in grain-handling and 
inflammable dust-producing plants. 

Boissevain, Manitoba, Canada 

On the evening of December 6, 1919, an explosion occurred in a 
flour mill at Boissevain, Manitoba, Canada (Fig. 16), resulting in a loss 
of about $15,000, and 
injury to one employee. 
The explosion, caused 
by the striking of a 
match in a flour bin, 
propagated up the stair- 
way and through other 
openings to the next 
floor above where a 
secondary explosion did 
extensive damage. The 
brick wall at one side of 
the mill was blown out 
and the warehouse was 
damaged. As the mill 
was quite clean, very 
little fire occurred. 



Buffalo, N. Y. 

On November 21, 
1919, an explosion oc- 
cured in an elevator leg 
of a Buffalo feed-grind- 
ing plant. 

At the time of the ex- 
I)losion workmen were 
using an oxy-acetylene 




Fig. 16. — Explosion blew out wall of upper floor after 
propagating from floor below. 

torch to cut an opening in the boot of an elevator leg. A man at the 
top of the leg was changing a spout leading from the elevator head to a 
steel conveyor. After as much of the steel casing had been cut out as 
was necessary, and the torch had been extinguished the men began to 
hammer the plate out of the opening. At the same time the man at the 
top of the elevator leg started to hammer on the short spout leading from 
the head. It is not known whether the torch had ignited the dust in the 
boot, causing it to smolder, or whether the hot plate ignited the dust, 
which had been stirred up by the hammering. The explosion that fol- 
lowed traveled up the back leg and burst it open for a distance of about 
30 feet, in spite of the fact that a portion of the leg was open and a vent 
provided. No fire followed the explosion but several employees were 
injured and the elevator leg was damaged. 



24 



Denver, Colo. 

A dust explosion followed by fire caused a loss of over $125,000 in 
a large Denver flour mill on January 20, 1920. • 

At first the cause of the explosion was ascribed to the production of 
sparks by a suction fan used in connection with the dust-collecting system. 
In the investigation of the explosion it was noted that the fan blades 
from which the spark was said to have originated were fastened to an 
overhanging fan shaft by means of a feather key held in place by set 
screws, with a one-inch clearance between the fan blades and the right- 
hand side of the outer fan casing, but none on the left-hand side of the 
casing. The theory that the key became loose in the fan shaft and per- 
mitted the revolving fan blades to strike the sides of the fan casing, thus 
producing sparks which in turn ignited the fine flour dust coming from 
the roll suction, was then advanced. Since the damage resulting from the 
explosion indicated that the ignition of dust took place in the dust-collect- 
ing system, it was decided that ignition could be attributed to the pres- 
ence of sparks either in the fan or from the rolls. On the strength of 
the evidence of a workman on the roll floor that one of the doors on the 
roll stands had been blown open, it seems reasonable to suppose that 
the* explosion originated within the rolls rather than in the fan. 



EXPERIMENTAL WORK 
Theory of Dust Explosions 

A misunderstanding seems to prevail among some as to what a dust 
explosion really is. These assume that dusts explode in the same man- 
ner as high explosives, that, for instance, a sack of flour or a package of 
starch in the kitchen cabinet might suddenly blow up as gunpowder 
might. This, however, is not the case, for dusts explode in the same 
way as gas does, not like gunpowder and other explosives. Just as gas 
and air must be intimately mixed, and in the proper proportions, in the 
cylinder of an internal combustion engine, so grain dust must be in sus- 
pension in the air as a cloud, intimately mixed with air, and in certain pro- 
portions. Neither the mixture of gas and air nor that of dust and air will 
explode until it comes in contact with a flame or some other source of 
heat of sufficient intensity to cause it to ignite. 

Density of Dust Cloud. — The minimum quantity of grain dust which 
must be in suspension before an explosion can be initiated has not yet 
been determined. It is reasonable to assume, however, that, since most 
of the grain dusts are more inflammable than coal dust, the density of a 
cloud of grain dust need not be greater than that of a cloud of coal dust 
through which an explosion will just propagate. The Bureau of Mines, 
of the United States Department of the Interior, has found this density 
in case of coal dust to be 0.0253 ounce of dust per cubic foot, while the 
French Experiment Station has shown that it is 0.023 ounce per cubic 
foot. 

25 



Source of Ignition. — To ignite most dusts it is not always necessary 
to bring them in contact with a large source of heat, such as an open 
flame, nor a very high temperature, such as an electric arc. Indeed, a 
number of explosions have resulted from the ignition of the dust by 
sparks struck as foreign materials passed through the machinery. A 
spark formed by the discharge of static electricity will ignite many, if not 
all, of the dusts under certain conditions. Some of the dusts are ignited 
when they come in contact with bodies having a temperature of 540 de- 
grees C. (1004° F,). which is well below dull red heat, and most of them 
will ignite when brought in contact with a body having a temperature 
slightly above 600 degrees C. (1112° F.). 

Velocity of Propagation of Explosion. — The velocity of propagation 
of explosions through most gas mixtures is more rapid than through most 
dust clouds, although in a few cases it has been found that the velocity 
of flame propagation in coal dust explosions has exceeded the maximum 
for certain gases. In only two tests has any attempt been made to meas- 
ure the velocity of propagation of the flame in clouds of materials other 
than coal dust. One indicated that the velocity through a cloud of wheat 
flour dust was practically the same as that through coal dust ; the other 
that the propagation through a cloud of powdered starch was several 
times as rapid as through the coal dust. These results, however, cannot 
be considered to be conclusive. 

Pressures Developed in Explosions. — As high pressures have been 
developed in coal dust explosions as in those of many of the gases. 
Higher pressures have resulted from the explosion of several of the grain 
dusts than from the explosion of coal dust. This indicates that certain 
grain dusts are more inflammable than coal dust, and quite as inflammable 
as many of the combustible gases, if not more so. 

Conditions for Explosion. — Although it is true that not all dusts 
will explode, the dusts from any material which burns, or is readily oxi- 
dized ,will explode under certain conditions. The ease of ignition de- 
pends upon various factors, such as the composition and fineness of the 
material and the amount of moisture in the dust. The composition of 
each dust, of course, is fixed, but its fineness and moisture content may 
vary. Speaking broadly, the finer the dust and the lower its moisture 
content, the more readily ignition takes place, or the greater the possi- 
bility of an explosion. This, however, should not be taken to mean that 
a coarse or a moist dust will not ignite. As a matter of fact, if the dust 
is fine enough and dry enough to form a cloud or to be thrown into sus- 
pension in the air, it can be ignited, and may propagate an explosion. 

Propagation of the Explosion. — When a plant is destroyed by an 
explosion a series of reports resembling a roll of thunder usually is 
heard. This is due to the fact that several explosions follow one another 
so rapidly that the report of one blends in with that of the next, making 
a continuous roar. For example, the original, or primary, explosion 

26 



may occur in a grinding machine where the dust cloud is confined within 
a small space. The pressure and percussion from this primary explosion 
throws into suspension the dust which has accumulated on beams, ledges, 
and floors. This dust is ignited by the flame of the primary explosion, 
giving rise to the second explosion, which, in turn, stirs up the dust in the 
surrounding portion of the plant. Thus the explosion is propagated 
throughout the plant, or as far as dust is held in suspension or capable 
of being thrown into suspension. 

PREVENTION OF EXPLOSIONS.— To prevent explosions, 
therefore, it is essential not only that all possible sources of ignition, 
such as open flames, the presence of foreign material in the grinding 
machines, an accumulation of static electricity, improper installation 
of electrical equipment, and an inadequate protection for all electrid 
lamps in a dusty atmosphere, be eliminated, but also that the plant be 
kept scrupulously clean, thus offering no medium of propagation of 
the primary explosion into the secondary, and more extensive, as well 
as more disastrous, explosion. 



Large Scale Tests 

Large scale tests on the explosions of grain dusts were conducted at 
the testing station of the Bureau of Mines at Bruceton, Pa., where a large 
steel gallery, 6 feet in diameter and 220 feet in length, with vents every 
few feet to relieve the pressures, is used in testing the inflammability of 
coal dusts. The grain dust tests were made under the same conditions as 
obtain in testing coal dust. 

One pound of dust to each linear foot of the gallery was spread on 
four shelves on both sides of the interior of the gallery. The dust was 
thrown suddenly into suspension and ignited at the closed end of the 
gallery, thus propagating the explosion well out through the open end. 

Ordinary wheat flour, corn starch, and a mixture of 60 per cent, flour 
and 40 per cent, shale dust (ash) were used, in addition to the coal dust. 

Flour and coal dust behaved alike, the explosions produced in each 
case being propagated at about the same velocity and developing approxi- 
mately the same pressure. The flame was propagated readily through 
the cloud produced from a mixture of flour and shale, but much less 
readily than in one from pure flour, and with but slight pressure. 

The explosion from the starch dust was the most violent of all, and 
developed pressures several times greater than those from the coal dust 
or flour. The rate of propagation also exceeded that in any of the other 
tests. Indeed, the percussion was so great that windows and dishes in 
buildings two or three miles distant were shaken, and employees of the 
station stated that it was the most violent explosion they had ever seen at 
the gallery. In considering the relative violence of the explosions from 
starch and from flour, it should be borne in mind that the flour was 
coarser than the starch and that its particles had a tendency to adhere. 

27 



Electrical Equipment and Dust Ex 

021 534 228 1 

Investigations of explosions in the various indusiries wiieie iiniaiii- 

mable dusts are created during the operating processes developed the 

relation of the electrical equipment and appliances to the cause of dust 

explosions. In some instances the explosions appeared to be due to the 

ignition of the dusts by electric sparks or the breaking of incandescent 

electric lamp bulbs in dust clouds. In the investigation of a very recent 

disastrous explosion resulting in large loss of life and extensive property 

damage, one of the probable causes suggested was the ignition of the dust 

in suspension by an electrical source. 

The lamp manufacturing companies were naturally very much inter- 
ested in this phase of the problem, and arrangements were made for co- 
operative experimental work relating to electric lighting equipment. 
Special tests are already in progress as a result of which it is hoped to 
determine the relation of electric lamp bulbs to explosion and fire and 
develop equipment which will afford extra protection. In the prelimi- 
nary tests already conducted, explosions were readily produced when 
incandescent lamp bulbs of all types were broken in dust clouds. 



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LIBRARY OF CONGRESS %| 

021 534 228 l! 



